The conformations, microdynamic behavior, and interactions with biologically important macromolecules of neurohypophysial peptide hormones, hypothalamic hormone releasing factors, and other biologically active peptides will be investigated. The peptides to be studied have important effects on cardiovascular, smooth muscle, and reproductive functions in mammals including man. The relationships between biological activity and the conformations and microdynamic behavior of the peptides will be sought. Partially deuterated neurohypophysial hormones, arginine-vasopressin and oxytocin, and related C14 and unlabeled derivatives will be prepared. Simplified preparations of deuterated amino acids will be studied. The deuterated hormones will be used to study the microdynamic behavior of these compounds, and the interaction of the hormones with their carrier proteins, the neurophysins. Deuterium(2H) NMR methods will be used for these studies along with other physical methods including carbon-13 NMR, equilibrium thin-film dialysis, and circular dichroism. Related studies on the hypothalamic peptides, luteinizing hormone releasing factor (LRF) and thyrotropin releasing factor (TRF), and the cardiovascular active peptides angiotensin-II and bradykinin will be made. These studies will seek to develop a physical-chemical basis for understanding the significance of the conformations and microdynamic behavior of these peptides in various biological contexts.